Thank you for your reply! I have 'Hans Heiling' on cd. I find it remarkable that Marschner's operas were overlooked by record labels,throughout the 60s and 70s,when lesser known operas of this quality were still being recorded in studios and would have garnered a suitably 'starry cast'.
Well, a large part of the problem affecting Marschner, I suspect, is that singspiel doesn't translate well to other countries. There's too much dialogue, which means non-native speakers will wrestle with it more so than native speakers. And with other composers it can be overcome by translation, but in Marschner's best work the dialogue is so integral a part of the piece that there's no way around it.
At least, that's always been a reason that I've suspected singspiele aren't performed more often outside their country of origin.